I don't have a rooting interest in the World Series, but I think Kansas City wins if the Mets starting pitching cannot generate enough swings and misses. The Royals are probably the best team in baseball at generating contact. They certainly thrive on facing power pitchers, which the Mets pitchers are. What was a dead giveaway to me was in Game 6 of the LCS against the Blue Jays.
David Price gave up two early home runs in the game, and then went to throwing a curve ball with greater frequency. Once he did that, the Royals were not as successful. It wasn't until they chased Price and got into the bullpen where they ended up winning the game (against power pitchers whose secondary pitches weren't as successful). The Royals are not a team that takes a lot of pitchers, which is part of their success. They are aggressive, but if a pitcher is crafty enough to adjust and throw more off-speed pitches, it makes the fastball much more effective. The Jays pitcher that had the most success was Marco Estrada. What he was able to do better than any of the other Jays pitchers is mix in his off-speed stuff with his fastball, which is average. But, when you throw those other pitches for strikes, it makes an average fastball way more effective.
The Mets will need to be successful using those secondary pitches to beat the Royals.
Conversely, the Royals need their starting pitching to be better, and go a little deeper into games. 4-5 inning starts are going to put more pressure on their bullpen, and as good as it has been, they can't be running out their bullpen every night. They will need a couple of starts where the starter goes 6-7 innings, and it makes their bullpen much more effective, and that's saying something because their bullpen is among the most effective in baseball.
In the end, I think the Royals are just a little better than the Mets and win the series in 6 or 7 games.